It is already known to permanently anchor a dental prosthesis in the jaw with the aid of titanium screws implanted in the jawbone. The screws are anchored in holes in the bone in such a way that the upper part of the screw is located levelled with or immediately below the top surface of the jawbone The screw is then covered over with a flap of mucous membrane and is left unloaded for a rest period of 3 to 6 months so that the bone can grow securely to and form a unit with the implanted screw. After the rest period the screw is exposed and a spacer element, preferably also made of titanium, is screwed into place, after which a dental prosthesis is anchored on the spacer element. The dental prosthesis must in this case be adapted accurately to the actual appearance of the jaw with the implanted titanium elements.
Swedish Patent 8701949-3 describes a device for anchoring a so-called single-tooth replacement on an implanted titanium element. In this case the spacer element consists of a spacer sleeve which is anchored on the titanium element with a special spacer screw which is provided with an externally threaded section which engages in a threaded bore in the upper part of the titanium element.
Swedish Design Application 892064 shows another type of spacer element with a conically designed base part which connects to the upper part of the titanium element and an upper, hexagonally designed column part, the whole component being made of titanium.
The base part of the titanium spacer can be designed in different lengths In this case a length is chosen which is such that the shoulder of the base part ends 1 to 3 mm under the surface of the gum, so that no titanium is visible after the crown has been cemented in place. The crown is designed so that it extends down to the shoulder of the spacer.
Before the crown is fitted, a certain period of incorporation is required in order for the gum swelling to go down. In addition, a certain time is needed in order to produce the final crown, since the latter must be manufactured individually for each patient.
During this period, when the manufacture of the crown and the incorporation take place, the gum must be kept away from the shoulder and the column part of the spacer. It is also important to shape the gum so that the crown, which in most cases is wider than the base section of the spacer, can be secured easily in place.
It is also advantageous if the pocket in the gum is slightly larger than the final crown. This in fact gives the dentist an opportunity to control the so-called cement seam which is produced when the crown is cemented or glued into place, for example using normal dental cement.
The mucous membrane normally contracts quickly around the crown when it has been fitted. Therefore it does not matter if the pocket in the gum is so large that space for clearing excess cement has been left after the cap has been removed.
Caps are previously known which are secured by means of a screw and whose main task is to protect the thread in which they are screwed tight. These previously known caps cannot however be used on the spacer elements which have been described above, since both the spacer and the screw holding the spacer in place have no internal thread. Adhesive or so-called temporary cement should not be used either, since it may be difficult to remove the cap and, if it has been successfully removed, there will still be laborious work involved in clearing away adhesive and cement residues.
Nor have these previously known caps been designed in such a way that a pocket has been formed in the mucous membrane, which pocket facilitates securing of the crown and inspection of the seam between the crown and the spacer.